yesterday I wanted to change my 12-25 to a 11-23 and I had troubles adjusting my rear derailleur so that that the chain would run smoothly on my 11. I tried everything up to adding/removing spacers (do you actually need spacers between your biggest cog and the wheel?).
It kept on bouncing up and down my 11 and regardless the adjustments I made on the derailleur it kept on doing the same. I changed it back to my 12-25 and no more troubles and it runs like butter....
wheelset: Zipp 404's (tubular)
Any thoughts what I do wrong?